1. Field of the Invention
The present invention relates to an ink cartridge for use in automatic marking systems for imprinting the surfaces of either stationary or moving articles or a moving web.
2. Description of the Prior Art
Prior art ink storing cartridges for use in automatic marking systems conventionally employ a reservoir container filled with an ink absorbing wick or absorbent filler material for transmitting ink from the interior of the reservoir container to an open outlet end thereof. One end of the wick or filler material is positioned at the open outlet end of the reservoir container so that as a transfer roller or print head contacts this end of the wick or filler, ink may be transferred therefrom to the roller or print head at the point of contact. If a transfer roller is used, ink transferred from the wick to the roller is then, in turn, transferred automatically to a print head. The print head contains a type face which is wetted with ink to imprint surfaces of articles or substrates that are passed by it. There are a number of disadvantages associated with use of the conventional ink cartridge which employs an ink absorbing wick or filler as the principal means of transmitting ink to its outlet.
One serious disadvantage of conventional cartridges is that since one end of the cartridge is exposed to the environment there is loss of significant amounts of ink through overfeeding and through evaporation. Therefore efforts have been made to cover the exposed end of the ink reservoir from the environment as much as possible. Since fast drying inks containing volatile solvents can be used in ink cartridges adapted to automatic marking systems, even slightly imperfect seals will result in substantial loss of ink. Typically, as much as 40 percent of the ink supply is lost to the environment either by evaporation or leakage when conventional cartridges are used. Since so large a percentage of ink is lost with the conventional cartridges, they tend to be bulkier in size in order to accommodate a larger supply of ink. Also, the conventional cartridges generally require recharging or replacement of the ink supply long before all the ink in the reservoir has been consumed.
Another problem encountered when ink is transmitted principally through capillary action is that the flow of ink is difficult to regulate as the ink supply diminishes within the container. Varying methods have been tried in an effort to maintain an even flow of ink at all stages of cartridge use. Conventional methods have included devices such as wiper blades which contact the surface of the transfer roller to regulate the ink film thickness and thus maintain the flow of ink at an even rate; but this method while regulating the ink flow tends to cause leakage of ink, thus leading to less efficient utilization of the ink supply. It is important to maintain the ink flow at a constant and optimum rate, to ensure print quality.
U.S. Pat. Nos. 3,797,390, 3,662,682, and 3,457,854 are illustrative of the prior art. In U.S. Pat. No. 3,797,390 an ink cartridge for automatic marking systems is disclosed. The ink storage device is essentially composed of an elongated container forming an ink reservoir with a sponge-like ink absorbing filler placed within the container to transmit ink by capillary action from the reservoir to an outlet end of the container. There is included a baffle spacing element beside the foam sponge-like filler to provide a reservoir portion in the bottom of the elongated container. The ink storage device additionally includes a porous felt disk pad which is of very thin construction compared to the foam filler. The felt disk pad is placed in contact with the exposed end of the foam filler and faces the outlet end of the ink storage device. An apertured closing disk is placed over the porous felt disk pad thus exposing a portion of the porous felt disk pad. This reference exemplifies the prior art, with the problems of ink evaporation, vacuum resistance to flow, nonuniform ink flow, and leakage.
U.S. Pat. No. 3,662,682 is further characteristic of prior art ink cartridges which utilize an absorbent filler material as the principal means of transmitting ink. In this reference, a transfer roller is in continuous contact with the exposed end of the absorbent foam filler. As the transfer roller revolves it is coated with ink from the absorbent filler. The transfer roller, in turn, transfers ink to a print head upon contact of the print head with the surface of the transfer roller. Since an absorbent filler is employed as a principal means of transmitting ink to the open end of the ink cartridge, there is great difficulty in regulating the flow of ink as ink is consumed. Various techniques have been employed in an attempt to solve the problem of diminishing ink flow, but with only limited success. The method disclosed in this reference for regulating ink flow is inclusion of a wiper blade which is made to contact the transfer roller under varying degress of pressure adjustable through a spring-like mounting element in contact with the wiper blade. This device poses the problem that the spring tension must be manually adjusted at varying stages as the ink is consumed. The wiper blade additionally does not completely solve the problem of irregular ink flow through the absorbent filler. Also, since the absorbent filler material is so close to the outlet end of the ink cartridge, there is still a persistent problem of high loss of ink from the absorbent filler due to overfeeding, surface evaporation, and leakage.
In U.S. Pat. No. 3,457,854, an ink cartridge for automatic marking systems is disclosed employing in concept elements similar to those disclosed in U.S. Pat. No. 3,662,682. The ink reservoir container is filled with an ink absorbing filler material which is employed as the principal means of transmitting ink by capillary action from the ink reservoir to an open outlet end thereof. A revolving transfer roller contacts an exposed surface of the filler. As disclosed in U.S. Pat. No. 3,662,682, a wiper roller is used to exert varying degrees of pressure on the transfer roller in order to attempt to regulate the flow of ink to the transfer roller and to maintain the ink flow at a constant level as ink in the reservoir is consumed. The wiper roller is adjusted manually by means of a screw which exerts a spring-like force. The wiper roller mechanism, however, is only partially effective in regulating ink flow as ink is consumed.
Accordingly, it is an object of the present invention to provide a disposable ink cartridge which incorporates a fast drying ink, but yet prevents significant loss of ink by evaporation or leakage.
It is an important object of the present invention to provide a disposable ink cartridge for automatic marking systems, which cartridge transmits a constant flow of ink to a print head or transfer roller in contact with the cartridge only as it is being used.
It is another object of the invention to provide an ink cartridge which feeds a constant supply of ink to a transfer roller or print head in contact therewith until the supply of ink in the cartridge is depleted.